1. Field of the Invention
The present invention relates to a solid state imaging device.
2. Description Related to the Prior Art
A digital camera and a digital video camera are in widespread use and they are provided with a solid state imaging device and a semiconductor memory. Further, an electronic apparatus such as a personal computer, a mobile phone, an electronic notepads or the like comes into include a solid state imaging device to provide an image-taking function.
In general, the solid state imaging device of CCD type or CMOS type is used. These types of solid state imaging devices have a packaged bare chip (image sensor chip). On one side of the bare chip, a light receiving section and a charge signal transfer section are formed. On the light receiving section, plural pixels (light receiving elements) are arranged in matrix. For packaging the bare chip, as described in Japanese Patent Laid-Open Publication No. 8-236739, the bare chip is mounted on a ceramic substrate or a BGA (Ball Grid Array) substrate, and contact terminals of the bare chip are connected to contact terminals of the substrate by wire bonding, and then a cover glass is attached on the substrate.
In general, an imaging circuit including the light receiving section and the charge signal transfer section is driven at a high clock frequency. Therefore, by electromagnetic waves (electromagnetic radiation noises) radiated from bonding wires which connect the bare chip to the package, other chips such as one for driving a sensor circuit possibly malfunction. In addition, the sensor circuit possibly malfunctions by electromagnetic radiation noises radiated from the other chips. By considering this problem, Japanese Patent Laid-Open Publication No. 2003-224218 discloses that a solid state imaging device is contained in an electromagnetic-wave absorbing package formed of an electromagnetic-wave absorbing material so as to absorb and block (be electromagnetically shielded from) the electromagnetic radiation noises radiated from inside or outside of the solid state imaging device.
By the way, recently, demand is increasing for a solid state imaging device of wafer level chip size package (hereinafter referred to as WLCSP type), which can be directly mounted on a circuit board in a digital camera and any other electronic apparatuses. The solid state imaging device of WLCSP type is obtained by fixing the image sensor and forming contact terminals during the semiconductor wafer process. Because the solid state imaging device of WLCSP type can be directly mounted on the circuit board and connected thereto by the wire bonding, the digital camera and other electronic apparatuses can be downsized. However, if the solid state imaging device of WLCSP type is contained in the electromagnetic-wave absorbing package of Japanese Patent Laid-Open Publication No. 2003-224218, the size of the solid state imaging device is enlarged. Accordingly, the merit of the solid state imaging device of WLCSP type, to allow for downsizing the digital camera and other electronic apparatuses, is lost.